We will develop a modern, computer-controlled electrical stimulator for performing functional mapping by cortical stimulation. The primary application is for use with patients who are candidates for surgery to control or eliminate occurrence of epileptic seizures. Other applications will include functional mapping to plan surgery for other brain diseases such as tumors and research on brain electrical stimulation to control seizures. The need and specifications for the system come from recommendations of an expert panel of clinical users who have been consulted throughout the conception and Phase I research and will continue to be consulted in Phase II. In Phase I, we solved key technical issues associated with the design of the electrical stimulator and EEG amplifiers to minimize the interference to the exquisitely sensitive EEG amplifiers caused by the relatively huge electrical stimulation pulses. In Phase II, we will utilize the knowledge gained in Phase I to build two prototype systems. These will be tested on epilepsy patients in the normal course of their hospitalization for pre-surgical evaluation. [unreadable] [unreadable]